Method of forming spacing ring for tubes in high temperature environment

ABSTRACT

A spacing ring for placement between a radially inwardly facing annular surface on a first member and a radially outwardly facing annular surface on a second member to maintain the first and second members in predetermined radially spaced relationship. The ring consists of a plurality of matted metal threads formed into an annular configuration. The ring has a radially inwardly facing surface to surroundingly engage the radially outwardly facing annular surface on the second member and a radially outwardly facing surface to be surroundingly engaged by the inwardly facing annular surface of the first member with the radially inwardly facing annular surface on the first member and the radially outwardly facing annular surface on the second member in axially overlapping relationship. The invention also contemplates a method of forming the spacing ring. The wool material is wrapped around an annular surface on a core bar. The wool material is both radially and axially compacted on the core bar with a predetermined compressive force.

CROSS REFERENCE

This is a divisional application of co-pending, application Ser. No.444,535 filed Dec. 1, 1989 now U.S. Pat. No. 5,056,832, entitled"Spacing Ring for Tubes in High Temperature Environment".

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to spacer rings for placement between hardtubular elements that are interfit, one within the other, to facilitaterelative shifting therebetween and, more particularly, to a ring formedfrom matted metal threads.

2. Background Art

There are many high temperature environments in which tubular metalelements/pipes are joined together by mating, one within the other. Oneexemplary environment is an automobile exhaust system wherein several ofthe exhaust components are so interconnected.

One problem that has plagued the automobile industry is that of noisegeneration between the mated tubular elements on the exhaust system.Differences in the heating and cooling rates for the cooperatingelements can cause relative shifting and rubbing together of adjacenthard metal surfaces thereon, which can generate significant noise.

It is known to employ a spacer element to maintain a predetermined gapbetween the facing surfaces to accommodate expansion and contraction ofthe elements, without rubbing therebetween, through the contemplatedoperating temperature range. One conventional spacer consists of a ringof wire mesh interposed between the radially outwardly facing surface ofthe inner element and the radially inwardly facing surface of the outerelement. This mesh material is made from a relatively heavy gauge, wovenwire. The formed ring is bonded to the inner element, as by welding.

There are several drawbacks with the above wire mesh spacer ring. First,the wire defining the mesh is sufficiently rigid that the ring isvirtually incompressible. Consequently, the ring lacks the flexibilitynecessary to accommodate dimensional variations in the elementsresulting from temperature changes.

A further drawback with the wire mesh ring of the prior art is that thewire of the mesh is so rigid that it is virtually impossible toaccurately conform the ring to the surfaces of the inner and outerelements between which it is interposed. The result is that certainpoints of the ring are rubbed against the inner surface of the outertube and themselves produce an undesirable grating noise when theelements shift.

A further problem with the prior art mesh ring results from spotwelding, which is the process generally used to affix the ring to theinner element. The spot welds deform the ring from its desiredcylindrical configuration. The result is a reduction in the contact areabetween the ring and facing surfaces of the elements and considerablenoise production when the elements shift.

Further, the wire mesh, because of its inability to conform to and fillthe region between the tubes, leaves a gap for the transmission of soundwaves. This problem is aggravated in the regions surrounding the welds.

Another attempted solution to the above problem has been the provisionof a radially projecting dimple on one of the inner and outer elements.The dimple maintains a desired spacing between the inner and outerelements. However, the dimple, as with the wire mesh ring, rubsundesirably on the surface against which it bears and itself createsnoise when the elements shift relative to each other.

SUMMARY OF THE INVENTION

The present invention is specifically directed to overcoming theabove-enumerated problems in a novel and simple manner.

According to the invention, a spacing ring is provided for placementbetween a radially inwardly facing annular surface on a first member anda radially outwardly facing annular surface on a second member tomaintain the radially facing surfaces on the first and second members ina predetermined spaced relationship. The ring consists of a plurality ofmatted metal threads formed into an annular configuration. The ring hasa radially inwardly facing surface to surroundingly engage the radiallyoutwardly facing annular surface on the second member and a radiallyoutwardly facing surface to be surroundingly engaged by the inwardlyfacing annular surface on the first member, with the radially inwardlyfacing annular surface on the first member and the radially outwardlyfacing annular surface on the second member in axially overlappingrelationship.

The inventive ring is sufficiently resilient that it will accommodateradial expansion and contraction of the first and second members. Thering readily conforms to the curvatures of both the radially inwardlyand outwardly facing surfaces between which it is interposed and therebyeffectively limits sound transmission through the space between theradially facing surfaces. The wool material is sufficiently soft that itwill deform readily in shear and guide relative shifting between thefirst and second members without the generation of grating noises. Atthe same time, the ring is sufficiently rigid that it will substantiallymaintain its shape and thereby the spacing between the radially facingsurfaces.

Preferably, the ring is formed from metal threads having a diameter inthe range of 50-100 microns, and preferably 80 microns. The preferredmaterial is stainless steel - SUS 434. Stainless steel maintains itsintegrity in high temperature environments, to which the ring isparticularly suited.

Optimum ring performance, in terms of 1) maintaining the desired spacingbetween members; 2) conforming to the annular surfaces of the joinedmembers; 3) deforming radially and in shear in response to expansion andcontraction of the members; and 4) sliding against the surface of theouter member without noise generation, is realized by utilizing acompressive force, during formation, sufficient to produce a density forthe ring threads of approximately 500 Kg/m³.

In a preferred form, the ring is defined by a plurality of turns of arope of the wool material. This facilitates wrapping of the materialabout a core.

The invention also contemplates a method of forming the spacing ring.According to the invention, the wool material is wrapped around anannular surface on a core bar. The wool material is both radially andaxially compacted on the core bar with a predetermined compressiveforce.

The preferred method is carried out by wrapping a plurality of turns ofthe mesh rope onto the core bar. A compacting roller is urged againstthe metal wool material on the core bar with a predetermined force. Thecore bar and compacting roller are then rotated relative to each otherso that a uniform compaction of the wool is effected about the perimeterof the core bar.

To effect axial compaction of the ring on the core bar, preferably threeinteracting mold parts are employed. The first part defines an axiallyfacing blocking shoulder against which one axial end of the ring can beabutted. A second mold member has an annular shoulder which is urgedbiasably toward the blocking shoulder to thereby compress the ringbetween the first and second mold parts. The third part, a barrel, hasan annular surface which surrounds the ring and controls radialdeformation of the wool material as the ring is axially compressed bythe first and second mold members.

The present invention further contemplates a method of establishing aspaced connection between a radially inwardly facing surface on a firstmember and an axially overlapping, radially outwardly facing surface ona second member.

According to the invention, the annular ring of wool material is placedin surrounding relationship with the outwardly facing surface on thesecond member. The first member is then positioned relative to thesecond member so that the radially inwardly facing surface on the firstmember surrounds the outwardly facing ring surface.

The ring member is fixed, preferably to the radially inwardly facingring surface. This can be accomplished by a number of techniques, andpreferably by a welding process. The weld may be a spot weld or a lineweld. If the spot weld is employed, one or more welds are provided andlocated preferably midway between the axial ends of the ring.

If line welds are employed, at least first and second welding lines areprovided at diametrically opposite portions of the ring and extend overthe axial extent of the ring.

Once the ring is welded in place, the first member can be deformedradially inwardly to compressibly capture the ring between the radiallyfacing surfaces on the first and second members. By deforming the firstmember as described, the ring deforms to substantially fill the spacebetween the radially facing surfaces on the first and second members andany gap/recess in the ring that may be created by the welding process.

The inventive ring is particularly useful in high temperatureenvironments, such as in an automobile exhaust system. However, it maybe used in any system, whether high temperature or not, to maintain adesired spacing between interconnected tubular elements that are mated,one within the other.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic, side elevation view of a vehicle engine andassociated exhaust system in which the present invention can beemployed;

FIG. 2 is a side elevation view of a prior art woven wire mesh spacerring in operative position on a tubular element/pipe;

FIGS. 3--3(b) show the successive steps in formation of the prior artspacer ring of FIG. 2:

FIG. 3 is an enlarged plan view of a section of a woven wire layer usedto form the ring of FIG. 2;

FIG. 3(a) is a perspective view of a plurality of wrapped layers of thematerial in FIG. 3 used to form the ring of FIG. 2; and

FIG. 3(b) is a perspective view of the prior art ring of FIG. 2 made byforming the wrapped layers of FIG. 3(a) into an annular shape;

FIG. 4 is a perspective view of a preferred form of spacing ringaccording to the present invention;

FIG. 5 is a side elevation view of an exemplary connection between firstand second tubular members/pipes, with the inventive ring in FIG. 4assembled therebetween;

FIGS. 6-9 show the successive steps in formation of the spacing ringaccording to the present invention:

FIG. 6 is a schematic representation of a shaving process for creatingmetal fibers to form the ring;

FIG. 7 is a perspective view of a core bar showing the step of windingand compacting the wool material, in rope form, around the core bar;

FIG. 8 is a side elevation view showing the step of radially compactingthe wool material on the core bar; and

FIG. 9 is a sectional, side elevation view of a compacting mold systemand showing the step of axially compressing the wool material on thecore bar;

FIG. 10 is a perspective view of a tubular member/pipe with theinventive ring thereon and being welded thereto;

FIG. 11 is a perspective view of the ring showing a preferred locationof spot welds used to affix the ring to the tubular member/pipe;

FIG. 12 is a perspective view of the inventive ring on a tubularmember/pipe with a plurality of line welds used to affix the ring to thetubular member/pipe;

FIG. 13 is an end elevation view of the ring and tubular member/pipe ofFIG. 12;

FIG. 14 is a side, sectional view of interconnected exhaust systemelements with the inventive spacing ring incorporated therein;

FIG. 15 is an enlarged, side elevation view of a part of a first andsecond of the exhaust system elements employing the inventive ring,during the assembly process; and

FIG. 16 is a view as in FIG. 15 with one of the first and secondelements compressed radially inwardly into assembled relationship withthe other of the first and second members and thereby compressiblycapturing the ring in its operative relationship with the other of thefirst and second members and thereby compressibly capturing the ring inits operative position.

DETAILED DESCRIPTION OF THE DRAWINGS

In FIG. 1, one exemplary environment for use of the present invention isdepicted. The system at 10 is a vehicle exhaust system and consists ofan engine 12, with an exhaust manifold 14, which communicates through aconduit 16 consecutively through a converter 18, a pre-muffler/resonator20 and a muffler 22. Gases from the muffler 22 are exhausted through atailpipe 24 away from the system 10.

The invention is concerned with the connection between cooperating maleand female tubular elements/pipes and, more particularly, with a ring at26 (FIG. 4) utilized to maintain a predetermined spacing betweeninterfitting male and female elements, identified generically as A and Bin FIG. 5. Spacing between the male and female elements A,B is requiredto accommodate expansion and contraction of the first and secondelements A, B and prevent direct contact and rubbing between theelements A, B as might generate noise upon the elements A, B shiftingrelative to each other.

It should be understood that while the invention can be used with anymale and female tube/pipe connection, and in any environment, it isparticularly adaptable to the high temperature exhaust systemenvironment of FIG. 1. The focus herein will be on an exemplaryconnection at one end 28 of the pre-muffler 20 (FIGS. 14-16).

The pre-muffler/resonator 20 consists of a front exhaust pipe 30 and arear exhaust pipe 31. The rear portion 32 of the front exhaust pipe 30is made porous as by the provision of a plurality of radially extendingthrough bores 34. An outer, cylindrical housing 36 surrounds the rearpipe portion 32 and is deformed radially inwardly at its front and rearends 38, 40, respectively, to define a reduced diameter collar 42 at itsfront end 38 and a reduced diameter collar 44 at its rear end 40. Anannular silencer chamber 46 is defined between the rear pipe portion 32and the housing 36.

The collar 42 is welded directly to the front exhaust pipe 30. The rearpipe 31 is fixed directly to the collar 44 as by welds 45 (FIG. 16). Thering 26 is interposed between the radially inwardly facing surface 48 onthe rear collar 44 and the radially outwardly facing surface 50 on therear pipe portion 32 so as to maintain a predetermined space 51therebetween.

Heretofore, it has been common to employ a ring, such as that shown at52 in FIGS. 2 and 3--3(b), to maintain the spacing between the collar 44and exhaust pipe portion portion 32. The ring 52 is constructed byforming a plurality of layers of a woven wire mesh material into anannular shape. The wire defining the mesh is generally 0.13 to 0.15millimeters in diameter, and is therefore quite rigid. Each layer, at54, is formed by weaving the wire 53 in the manner shown in FIG. 3. Thewoven wire material is then wrapped about itself, as shown in FIG. 3(a),to produce a plurality of layers L --in this case six, with a desiredwidth W for the ring 52. The preformed element in FIG. 3(a) is thenformed into the annular shape of FIG. 3(b) to complete the ring 52. Thering 52 is placed around and affixed to the pipe portion 32 as by spotwelding. One spot weld 55 is shown in FIG. 2, however four spot weldsare commonly used. The layers 54 of the ring 52 are oriented so that thelines L1 (one shown) bisecting the generally horseshoe-shaped loops 56defined by the weaving process, are oriented at approximately a 45#angle with respect to the longitudinal axis 57 of the pipe portion 32.

The difficulty with the prior art woven mesh ring 52 is that it issufficiently rigid that it is not only difficult to make, but it doesnot accurately conform to the annular surfaces 50 (one shown) betweenwhich it resides and affords little cushion between the exhaust pipeportion 32 and collar 44. The wire, which is commonly stainless steel,produces a grating noise as it rubs against the inside surface 48 of thecollar 44. Still further, the spot welds 55 create air gaps and furtherdeform the ring 52 from its preferred annular shape. The presentinvention overcomes these drawbacks.

According to the present invention, the ring 26 is formed from mattedmetal threads/wires. Preferably the threads have a diameter in the rangeof 50-100 microns, with a preferred diameter of 80 microns. Preferably,the thread material is stainless steel - SUS 434.

According to the invention, the wool material is compacted under apredetermined pressure to produce the annular configuration of FIG. 4.The compaction pressure is sufficient to produce a density for the ringthreads of approximately 500 Kg/m³, but may be varied depending upon theparticular demands of the environment and the particular application forthe ring 26. This pressure compacts the threads sufficiently that thering 26 will maintain its shape. At the same time, the ring remainsresilient enough to conform to the surfaces between which it iscaptured, and flex in response to relative movement between the collar44 and exhaust pipe portion 32. The outer surface of the ring 26 issoft, because of the woolly nature of the material from which it ismade, and slides silently against the collar 44. Further, the ring 26deforms readily in shear upon the collar 44 and pipe 32 moving relativeto each other.

Once the ring 26 is formed, it is placed in surrounding relationshipwith the rear exhaust pipe portion 32, as seen in FIGS. 12, 14 and 15and affixed thereto, preferably by welding. The pre-muffler housing 36is then deformed from the FIG. 15 configuration radially inwardly, as bya swaging process, to define the collar 44 and a tapering neck 54connecting between the constant diameter body 56 of the housing 36 andthe collar 44, to complete the pre-muffler subassembly 20, as shown inFIG. 16.

Process for Forming the Ring 26

The individual wires/threads 58 making up the ring 26 can be formed byshaving a piece of stainless steel stock 60, as shown in FIG. 6. Aconventional shaving tool 62 engages the stock 60 and causes theindividual wires/threads 58 to be separated therefrom as the stock 60 ustranslated relative to the tool 62 in the direction of arrow 64. Amultitude of wires 58 is then accumulated into a manageable rope 64, asshown in FIG. 7. The rope 64 is wrapped around a cylindrical core bar 66having a diameter D2 (FIG. 7) that is slightly larger than the diameterD1 (FIG. 16) of the outer surface 50 of the exhaust pipe portion 32.Exemplary dimensions are as follows:

D1 (for the exhaust pipe portion 32 - FIG. 16) =50.8 mm.

D2 (for the core bar 66 - FIG. 7) =52 mm.

D3 (for the ring 26 - FIG. 15) =56 mm.

These dimensions should be viewed as limiting and are given only by wayof example.

The rope 64 is wrapped against the outer surface 68 of the core bar 66,preferably by rotating the core bar 66 about its length, as indicated byarrow 70 in FIG. 7. As the rope 64 is being wrapped on the core bar 66,a compacting roller 72, as shown in FIG. 8, is pressed against the woolon the bar 66 and oppositely rotated in the direction of arrow 71 toradially compact the wool material against the core bar 66. The core bar66 and compacting roller 72 are rotatable about spaced, parallel axes74, 76, respectively. The compacting roller 72 is urged against the woolmaterial with a predetermined force. Relative rotation of the core bar66 and compacting roller 72 in the direction of arrows 78, 80 (FIG. 8)then effects an even compaction of the wool around the periphery of thecore bar 66 to a desire thickness T.

Once the wool material is compacted suitably in a radial direction,axial compaction of the ring 26 is effected, and preferably through amold system such as that shown in FIG. 9. A first mold part 82 having astepped body 84 and a bore 86 therethrough is slid over the end 88 ofthe core bar 66.

The one portion 90 of the mold part 82 defines an annular blockingshoulder 92, which abuts one end 94 of the ring 26 on the core bar 66. Asecond mold part 96, having an annular configuration, is slid over theopposite end 98 of the core bar 66 and has an annular shoulder 100 whichcan be borne against the opposite ring end 102.

With the mold part 82 held fixed on the core bar 66, the mold part 96can be urged towards the mold part 82 to compress the ring 26 in anaxial direction. Movement of the mold part 96 towards the mold part 82can be effected through a plunger 104 biased in the direction of arrow106.

To prevent radial bulging of the ring 26 and guide translation of themold part 96, a sleeve-like barrel 108 is provided and surrounds theouter surfaces 110, 112 of the mold parts 82, 96.

Once the ring 26 is formed to the desired shape, the mold parts 82, 96are slid to the left in FIG. 9 relative to the barrel 108 and core bar66. The ring 26 is thereby released.

Attachment of the Ring 26

Once the ring 26 is formed, it is placed over the exhaust pipe portion32 in a position spaced slightly from the rear edge 111 (FIG. 15) of thepipe portion 32. Placement of the ring 26 is facilitated by having theinside diameter D2 thereof slightly larger than the outside diameter D1of the pipe portion 32. Through a conventional welding mechanism at 112(FIG. 10), spot welds 114, 116 are formed, as shown in FIG. 11, oralternatively, axial weld beads/lines 118, 120, 122, 124 are formed toeffect connection of the ring 26 to the outer surface 50 of the pipeportion 32.

If spot welding is performed, preferably three or four such welds 114,116 (two shown) are located axially at the midportion of the ring 26. Ascan be seen in FIG. 11, the weld 116 is located so that the distances X1and X2 from the one ring end 94 and the other ring end 102,respectively, are equal.

If lines of welding, as in FIGS. 12 and 13 are formed, preferably thelines 118, 120, 122, 124 are equidistantly spaced around the peripheryof the ring 26 and pipe portion 32. As can be seen in FIG. 13, the welds118, 120, 122, 124 cause the ring 26 to be deformed radially inwardly soas to define inwardly projecting, elongate ribs 126, 128, 130, 132 whichcontact the outer surface 50 of the pipe portion 32. The result is thatthere are slight indentations 134, 136, 138, 140 around the outerperiphery of the ring 26 and an annular space 142 between the radiallyinwardly facing surface 144 of the ring 26 and the radially outwardlyfacing surface 50 of the exhaust pipe portion 32.

The housing 36 is then placed in the FIG. 15 position relative to thepipe portion 32, and deformed by a swaging operation to the FIG. 16configuration. As the inside surface 48 of the housing 36 is deformed,it compresses the ring 26 from the FIG. 15 position to a slightlyreduced diameter D4, preferably on the order of 54.8 mm. As this occurs,the wool material collapses into the indents 134, 136, 138, 140 andcollapses into and fills the space 142. If spot welding is employed, thecompression of the ring 26 by the collar 44 will fill any voids/dimplescreated by the spot welds 114, 116 and fill the corresponding space 142.

The ring 26 maintains sufficient resilience that it allows for relativemovement between the housing 36 and pipe portion 32. The wool material,even though made of stainless steel, has a soft surface that will notgrate against the pipe portion 32 and produce undesirable noise. At thesame time, the ring 26 is sufficiently rigid that the desired spacingbetween the housing 36 and pipe portion 32 is maintained. The steelmaterial is resistant to the high temperatures contemplated in thevehicle exhaust system environment.

The invention contemplates the use of the ring 26 not only in theautomobile environment, but in any environment wherein there arecooperating, cylindrical first and second members, such as those A, B inFIG. 5, which are assembled, one within the other.

The foregoing disclosure of specific embodiments is intended to beillustrative of the broad concepts comprehended by the invention.

What is claimed:
 1. A method of forming a spacing ring for placementbetween a radially inwardly facing annular surface on a first member soas to maintain said first and second members in predetermined radiallyspaced relationship, said method comprising the steps of:providing ametal wool material consisting of a plurality of matted metal threads;wrapping the metal wool material around an annular surface on a corebar; and compressing the wool material on the core bar into an annularconfiguration with a radially inwardly facing annular surface and aradially outwardly facing annular surface, with each said ring surfacehaving a predetermined diameter.
 2. The method of forming a spacing ringaccording to claim 1 including the step of radially compacting the metalwool material with a predetermined pressure against said core bar. 3.The method of forming a spacing ring according to claim 2 including thestep of axially compacting the metal wool material.
 4. The method offorming a spacing ring according to claim 3 including the steps ofproviding a first mold part on said core bar with a blocking shoulder atone axial end of the ring, providing a second mold part with an annularshoulder and urging the annular shoulder on the second mold part againstthe ring on the core bar towards the blocking shoulder with apredetermined force to thereby axially compress the wool material on thecore bar.
 5. The method of forming a spacing ring according to claim 2including the step of axially compacting the wool material on the corebar after the wool material has been radially compacted.
 6. The methodof forming a spacing ring according to claim 5 wherein an annular barrelwith a radially inwardly facing surface is provided and including thestep of situating the barrel over the core bar so that the inwardlyfacing barrel surface is in surrounding relationship with the woolmaterial on the core bar to control radial deformation of the woolmaterial as the wool material is axially compacted.
 7. The method offorming a spacing ring according to claim 2 wherein the radial pressureexerted on the metal wool material on the core bar is sufficient toproduce a density for the ring threads of approximately 500 Kg/m³. 8.The method of forming a spacing ring according to claim 1 wherein themetal threads are made from stainless steel.
 9. The method of forming aspacing ring according to claim 1 wherein the metal threads have adiameter in the range of 50-100 microns.
 10. A method of forming aspacing ring for placement between a radially inwardly facing annularsurface on a first member and a radially outwardly facing annularsurface on a second member so as to maintain said first and secondmembers in predetermined radially spaced relationship, said methodcomprising the steps of:providing a metal wool material consisting of aplurality of matted metal threads; compressing the wool material into anannular configuration with a radially inwardly facing annular surfaceand a radially outwardly facing annular surface, with each said ringsurface having a predetermined diameter; wrapping the metal woolmaterial around an annular surface on a core bar; radially compactingthe metal wool material with a predetermined pressure against said corebar; and biasing a compacting roller against the metal wool material onthe core bar with a predetermined pressure and effecting relativerotation between the core bar and compacting roller to uniformly compactthe wool material about the perimeter of the core bar.
 11. A method offorming a spacing ring for placement between a radially inwardly facingannular surface on a first member and a radially outwardly facingannular surface on a second member so as to maintain said first andsecond members in predetermined radially spaced relationship, saidmethod comprising the steps of:providing a metal wool materialconsisting of a plurality of matted metal threads; compressing the woolmaterial into an annular configuration with a radially inwardly facingannular surface and a radially outwardly facing annular surface, witheach said ring surface having a predetermined diameter; wrapping themetal wool material around an annular surface on a core bar; andpreforming the wool material into a rope and wrapping a plurality ofturns of the rope around the core bar before compacting the woolmaterial on the core bar.